1. Field of the Invention
The invention relates to a process for cooling an auto-ignition combustion chamber.
2. Discussion of Background
In the combustion chambers used hitherto in gas-turbine construction, almost the entire mass flow of air of the compressor can be utilized to cool the combustion-chamber walls for the purpose of avoiding excessively high material temperatures. Only a small fraction of this mass flow of air passes into the combustion chamber, without previously having been employed for cooling. In such a type of cooling, the optimization of the cooling lies in working with as small a pressure loss as possible along the cooling stage, so that the efficiency of the gas-turbine plant does not suffer any collapse.
In contrast, in an auto-ignition combustion chamber which takes effect preferably downstream of a first turbine, its smoke gases naturally cannot be employed for cooling purposes on account of the prevailing high temperature. On the other hand, such a combustion chamber already undergoes a high heat load in the inflow zone, so that, even there, cooling has to be extremely efficient. The same also applies increasingly to the downstream combustion zone, where an even higher heat load prevails. In view of this, a high mass flow of air at low temperature would have to be extracted from the process for the purpose of cooling such an auto-ignition combustion chamber. It is necessary, at the same time, to bear in mind that gas-turbine sets of the current high-performance class can generally release only a little air for cooling purposes, since the efficiency and specific power would otherwise drop markedly. This has repeatedly given rise to proposals which postulate a cooling of the assemblies subject to a high heat load by means of other media from outside. First and foremost is the proposal to carry out the cooling by means of steam. If the gas-turbine set is integrated into a combination plant having a steam circuit, then such proposals are certainly worth examining. However, where no steam or media otherwise suitable for cooling exists, a cooling of the auto-ignition combustion chamber can be obtained only at the expense of losses of efficiency.